1. Field of the Invention
The present invention relates to magnetic sensors using a tunnel effect, which sensors are mounted in hard disc devices, other magnetic sensing devices and the like, and more particularly, the invention relates to a tunnel-effect type magnetic sensor capable of increasing a resistance change rate (ΔR/R).
2. Description of the Related Art
A tunnel-effect type magnetic sensor (TMR element) is a sensor which changes its resistance using a tunnel effect, in which when the magnetization of a fixed magnetic layer and that of a free magnetic layer are antiparallel to each other. A tunnel current is unlikely to flow through an insulating barrier layer (tunnel barrier layer) provided between the fixed magnetic layer and the free magnetic layer, so that the electrical resistance is maximized, and when the magnetization of the fixed magnetic layer and that of the free magnetic layer are parallel to each other, the tunnel current is most likely to flow, so that the electrical resistance is minimized.
By using the above principle, the change in electrical resistance by the change in magnetization of the free magnetic layer, which is caused by influence of an exterior magnetic field, is detected as the change in electrical voltage, so that a magnetic field leakage from a recording medium is detected. Related art is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 2006-261637 (hereinafter referred to as “Patent Document 1”)
In Patent Document 1, a tunnel-effect type magnetic sensor has been disclosed in which a free magnetic layer has a laminated ferrimagnetic structure.
According to Patent Document 1, in order to generate a sufficiently large exchange coupling between ferromagnetic layers which form the free magnetic layer, a first orientation control buffer is formed in one of the ferromagnetic layers. For example, in paragraph [0139]of Patent Document 1, an example has been disclosed in which Ni81Fe19 (2 nm), Ta (0.4 nm), Ni81Fe19 (2 nm), Ru (2.1 nm), and Ni81Fe19 (4 nm) are laminated in that order from the bottom to form the free magnetic layer.
However, in the invention disclosed in Patent Document 1, the structure for increasing the resistance change rate (ΔR/R) has not been disclosed.